In the case of carrying out drying or solid phase polymerization of Polymer particles by a batchwise system, there is widely adopted a tumbler type apparatus in which liquid phase polymerization polymer as the raw material is charged in a hermetically sealed vessel, and is heated while being rotated together with the vessel in an atmosphere of inert gas or under reduced pressure. The above-mentioned apparatus is generally of such structure that a suction/exhaust port for inert gas introduction or vacuum and a thermometer for measuring pellet temperature are fixed for the sake of convenience of each piping and wiring, whereby only the vessel rotates, and that rotational sealing portions are sealed with a packing for the purpose of preventing moisture or oxygen leaking on the inside of the vessel.
However, the sealing packing is worn by the contact between surrounding structures and Polymer particles owing to repeated drying or solid phase polymerization, and fragments thereof as foreign matters contaminate the objective product, thereby raising a problem of quality deterioration. As a method for preventing the contamination, periodical inspection and replacement of the packing are taken into consideration, but the packing-fitted portion is on the inside of the vessel. Thus it is accompanied with a definite time of shutdown of the apparatus to confirm the progress of packing wear or carry out replacement work, whereby frequent replacement thereof becomes problematic in production cost.
As a method for removing contaminated packing from the product, sorting and removal by means of a color sorting machine or the like are taken into consideration, but raise a problem of the increase in cost such as fixed cost and maintenance cost accompanying the introduction of the sorting machine.
Japanese Patent Laid-Open Application No. 136965/1997 (Heisei 9) discloses a batchwise solid phase polymerization apparatus which controls the reactional conditions by detecting the degree of vacuum inside a hermetically sealed reaction vessel using communication signals from a pressure receiver equipped on the inside of the vessel. Nevertheless nothing is mentioned in the above-mentioned literature in regard to temperature measurement in the vessel nor trouble of foreign matter generation.
As mentioned above, no literature is found regarding a method for solving the trouble of contamination by foreign matters for which the wear of sealing packing is primarily responsible in relation to batchwise drying and solid phase polymerization apparatus. Under such circumstances, it has been eagerly desired to develop a method for solving such trouble.
In such circumstances, the present invention is concerned with an apparatus for the purpose of drying or solid phase polymerization of Polymer particles by batchwise heating the same in an atmosphere of inert gas or under reduced pressure, and an object thereof is to provide a batchwise heating apparatus which is capable of efficient production by preventing objective product from being contaminated by foreign matters accompanying the wear of a sealing packing.